PEDIATRIC ANESTHESIA Section Editor Paul R. Hickey
Comparative Hernodynamic Depression of Halothane Versus Isoflurane in Neonates and Infants: An Echocar diographic Study David J. Murray, MD, Robert B. Forbes, MD, and Larry T. Mahoney,
MD
Departments of Anesthesia and Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa
The purpose of this study was to measure and compare the relationship of cardiovascular depression and dose during equal potent levels of halothane and isoflurane anesthesia in neonates (n = 19) (16.7 2 6.9 days) and infants (n = 54) (6.1 t 3.1 mo). Seventy-three children had heart rate, arterial blood pressure, and pulsed Doppler pulmonary blood flow velocity as well as two-dimensional echocardiographic assessments of left ventricular area and length recorded just before anesthesia induction. Anesthesia was induced by inhalation of increasing inspired concentrations of halothane or isoflurane in oxygen using a pediatric circle system and mask. During controlled ventilation, halothane and isoflurane concentrations were adjusted to maintain 1.0 MAC and then 1.5 MAC (corrected for age), and echocardiographicand hemodynamic measurements were repeated. A final cardiovascular measurement was recorded after intravenous administration of 0.02 mgkg of atropine. All measurements were completed before tracheal intubation and the start of elective surgery. In neonates, 1.0 MAC concentrations of halothane and isoflurane decreased cardiac output (74% 16%),stroke volume (75% 2 15%), and ejection fraction (76% 15%) similarly from awake levels. Decreases in cardiac output, stroke volume, and ejection fraction with halothane and isoflurane were significantly larger at 1.5 MAC
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omparative in vitro and in vivo cardiovascular studies in young versus older animals indicate that the immature, developing cardiovascular system is more sensitive to depression by inhaled anesthetics (1-5). Cardiovascular sensitivity is cited as a contributing factor to a higher incidence of anesthesia-related human cardiac arrests during infancy (6-8).The increased incidence of bradycardia, Supported by a grant from the Foundation for Anesthesia Education and Research (FAER), 1988. Accepted for publication October 17, 1991. Address correspondence to Dr. Murray, University of Iowa College of Medicine, Department of Anesthesia and Pediatrics, Iowa City, IA 52242. 81992 by the International Anesthesia Research Society ooo3-2959/92/~.00
(-35% decreases from awake values) than at 1.0 MAC. Heart rate decreased significantly during 1.5 MAC halothane anesthesia (94% 4%) but remained unchanged during isoflurane anesthesia. In infants, 1.0 MAC halothane and isoflurane decreased cardiac output (83% ? 12%),stroke volume (78% 2 12%), and ejection fraction (74% 12%) when compared with awake measures. Heart rate decreased during 1.0 MAC halothane anesthesia but increased during 1.0 MAC isoflurane. When anesthetic concentrations were increased to 1.5 MAC, stroke volume (71% 12%of awake) and ejection fraction (64% 2 13%of awake) decreased similarly from the 1.0 MAC measurement in both groups. When compared with 1.0 MAC, heart rate decreased further at 1.5 MAC halothane anesthesia (80% 2 5% of awake) but remained unchanged during 1.5 MAC isoflurane anesthesia (106%f 4% of awake). Atropine (0.02 mg/kg) increased heart rate and cardiac output by 15%-20% from measurements at 1.5 MAC halothane and isoflurane anesthesia in neonates and infants, but stroke volume and ejection fraction remained unchanged from measurements before atropine administration in both groups. Equipotent halothane and isoflurane produced similar hemodynamic depression in neonates and infants.
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(Anesth Analg 1992;74:329-37)
hypotension, and cardiac arrest in infants less than 12 mo of age when compared with adults suggests hemodynamic sensitivity to inhaled anesthetics extends from birth throughout the first year (6-11). Neonates are believed to be the most susceptible to hemodynamic depression from inhaled anesthetics, but major surgery during the neonatal period may also contribute to the increased incidence of anesthesia-related complications (11). Most clinical studies in pediatric patients that report greater hernodynamic sensitivity are based on cardiovascular measures at stable inspired halothane or isoflurane concentrations rather than end-tidal concentrations (12-14). The purported sensitivity of Anesth Analg 1992;74:329-37 329
330
PEDIATRIC ANESTHESIA MURRAY ET AL. HEMODYNAMIC DEPRESSION DURING ANESTHESIA IN NEONATES AND INFANTS
neonates and infants to inhaled anesthetics may be a function of uptake and distribution differences rather than greater susceptibility to myocardial depression (15). When equal inspired concentrations of halothane and isoflurane are administered, higher partial pressures of volatile anesthetics in brain and myocardium are more rapidly achieved in neonates and infants than adults because of a relatively larger vessel-rich tissue group and lower volatile anesthetic tissue solubility in the young compared with the adult (15,16). In neonates and infants, heart rate and systolic blood pressure measurements at 1.O MAC halothane anesthesia do not confirm speculations of increased hemodynamic sensitivity (17). When additional cardiovascular determinants have been measured during equal MAC halothane or isoflurane administration, the study population included older infants and small children (mean age = 12 mo) (18). The purpose of this study was to obtain dose-response measures of hemodynamic depression and to compare the cardiovascular changes at equipotent (equal MAC) concentrations of halothane versus isoflurane in separate groups of healthy neonates (
Comparative Hernodynamic Depression of Halothane Versus Isoflurane in Neonates and Infants: An Echocar diographic Study David J. Murray, MD, Robert B. Forbes, MD, and Larry T. Mahoney,
MD
Departments of Anesthesia and Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa
The purpose of this study was to measure and compare the relationship of cardiovascular depression and dose during equal potent levels of halothane and isoflurane anesthesia in neonates (n = 19) (16.7 2 6.9 days) and infants (n = 54) (6.1 t 3.1 mo). Seventy-three children had heart rate, arterial blood pressure, and pulsed Doppler pulmonary blood flow velocity as well as two-dimensional echocardiographic assessments of left ventricular area and length recorded just before anesthesia induction. Anesthesia was induced by inhalation of increasing inspired concentrations of halothane or isoflurane in oxygen using a pediatric circle system and mask. During controlled ventilation, halothane and isoflurane concentrations were adjusted to maintain 1.0 MAC and then 1.5 MAC (corrected for age), and echocardiographicand hemodynamic measurements were repeated. A final cardiovascular measurement was recorded after intravenous administration of 0.02 mgkg of atropine. All measurements were completed before tracheal intubation and the start of elective surgery. In neonates, 1.0 MAC concentrations of halothane and isoflurane decreased cardiac output (74% 16%),stroke volume (75% 2 15%), and ejection fraction (76% 15%) similarly from awake levels. Decreases in cardiac output, stroke volume, and ejection fraction with halothane and isoflurane were significantly larger at 1.5 MAC
*
*
C
omparative in vitro and in vivo cardiovascular studies in young versus older animals indicate that the immature, developing cardiovascular system is more sensitive to depression by inhaled anesthetics (1-5). Cardiovascular sensitivity is cited as a contributing factor to a higher incidence of anesthesia-related human cardiac arrests during infancy (6-8).The increased incidence of bradycardia, Supported by a grant from the Foundation for Anesthesia Education and Research (FAER), 1988. Accepted for publication October 17, 1991. Address correspondence to Dr. Murray, University of Iowa College of Medicine, Department of Anesthesia and Pediatrics, Iowa City, IA 52242. 81992 by the International Anesthesia Research Society ooo3-2959/92/~.00
(-35% decreases from awake values) than at 1.0 MAC. Heart rate decreased significantly during 1.5 MAC halothane anesthesia (94% 4%) but remained unchanged during isoflurane anesthesia. In infants, 1.0 MAC halothane and isoflurane decreased cardiac output (83% ? 12%),stroke volume (78% 2 12%), and ejection fraction (74% 12%) when compared with awake measures. Heart rate decreased during 1.0 MAC halothane anesthesia but increased during 1.0 MAC isoflurane. When anesthetic concentrations were increased to 1.5 MAC, stroke volume (71% 12%of awake) and ejection fraction (64% 2 13%of awake) decreased similarly from the 1.0 MAC measurement in both groups. When compared with 1.0 MAC, heart rate decreased further at 1.5 MAC halothane anesthesia (80% 2 5% of awake) but remained unchanged during 1.5 MAC isoflurane anesthesia (106%f 4% of awake). Atropine (0.02 mg/kg) increased heart rate and cardiac output by 15%-20% from measurements at 1.5 MAC halothane and isoflurane anesthesia in neonates and infants, but stroke volume and ejection fraction remained unchanged from measurements before atropine administration in both groups. Equipotent halothane and isoflurane produced similar hemodynamic depression in neonates and infants.
*
*
*
(Anesth Analg 1992;74:329-37)
hypotension, and cardiac arrest in infants less than 12 mo of age when compared with adults suggests hemodynamic sensitivity to inhaled anesthetics extends from birth throughout the first year (6-11). Neonates are believed to be the most susceptible to hemodynamic depression from inhaled anesthetics, but major surgery during the neonatal period may also contribute to the increased incidence of anesthesia-related complications (11). Most clinical studies in pediatric patients that report greater hernodynamic sensitivity are based on cardiovascular measures at stable inspired halothane or isoflurane concentrations rather than end-tidal concentrations (12-14). The purported sensitivity of Anesth Analg 1992;74:329-37 329
330
PEDIATRIC ANESTHESIA MURRAY ET AL. HEMODYNAMIC DEPRESSION DURING ANESTHESIA IN NEONATES AND INFANTS
neonates and infants to inhaled anesthetics may be a function of uptake and distribution differences rather than greater susceptibility to myocardial depression (15). When equal inspired concentrations of halothane and isoflurane are administered, higher partial pressures of volatile anesthetics in brain and myocardium are more rapidly achieved in neonates and infants than adults because of a relatively larger vessel-rich tissue group and lower volatile anesthetic tissue solubility in the young compared with the adult (15,16). In neonates and infants, heart rate and systolic blood pressure measurements at 1.O MAC halothane anesthesia do not confirm speculations of increased hemodynamic sensitivity (17). When additional cardiovascular determinants have been measured during equal MAC halothane or isoflurane administration, the study population included older infants and small children (mean age = 12 mo) (18). The purpose of this study was to obtain dose-response measures of hemodynamic depression and to compare the cardiovascular changes at equipotent (equal MAC) concentrations of halothane versus isoflurane in separate groups of healthy neonates (
